The long-term goal of this project is to improve our understanding of redox regulation of an intracellular calcium release channel (the ryanodine receptor) in skeletal muscle by reactive nitrogen species (RNS). All three isoforms of nitric oxide synthase (NOS) have been identified in skeletal muscle. Nitric oxide and related species (collectively termed reactive nitrogen species) produced endogenously in muscle have been shown to influence force generation. We hypothesize that the effects of RNS on muscle contractility occur in part through the ryanodine receptor, which contains regulatory thiols. The specific aims of this proposal are: 1) Define the subcellular locations of each isoform of NOS in relation to the ryanodine receptor 2) Assess the effects of reactive nitrogen species on channel activity in vitro and in muscle cell culture systems and 3) Determine the underlying molecular mechanism(s) of regulation. Our results may lead to new insights into regulation of Ca2+ homeostasis in muscle and to the dysregulation of Ca2+ characteristic of disease states such as respiratory failure and rhabdomyolysis.